Known centrifugal pumps comprise a rotor having impeller blades which is driven in rotation within a casing having an axial inlet for fluid and a peripheral outlet through which the fluid is discharged under the action of the rotor blades. Such pumps are generally designed to operate using only one direction of rotation of the rotor and the blades are shaped and angled to give an efficient pumping action when the rotor is driven in that direction. These pumps are usually very inefficient if the direction of rotation of the rotor is reversed, so that the blades are moving backwards.
In automatic underwater cleaners for swimming pools and the like, a submerged centrifugal pump is driven by an electric motor and is mounted on a device which is movable in more than one direction. Separate motors are provided for operating the pump and for driving the device in movement, the pump motor being operated in one direction only and the other motor being reversible so that the device can be moved in opposite directions as required.
The present invention is intended to provide a centrifugal pump which can operate efficiently when driven in either direction. Such a pump allows an automatic pool cleaner of the above-mentioned type to be driven by only one motor.
The blades of a centrifugal pump have to be set to particular orientations on the pump rotor to give an efficient pumping action. This orientation may vary according to the pressure against which the pump has to operate and according to the volume of fluid to be pumped. Also when designing a pump for a particular application, determining the optimum orientation of the impeller blades may be a troublesome and expensive operation.
The present invention is also intended to provide a centrifugal pump in which the blade orientation may readily be varied, and the optimum orientation easily determined.